The invention relates to a method for the elimination of remanence phenomena in reception systems and a device for the implementation of the method, in which flux pickups with ferromagnetic properties, preferably Hall generators provided with antennas, are provided for the detection of a field flux or, respectively, of a change of field flux proceeding from a field generator.
In reception systems in which, in particular, relatively small field changes are to be detected with the assistance of flux pickups such as Hall generators, and in which reproducible measuring results are to be achieved with signals gained from a change of field flux, no disruptive remanence phenomena having a negative influence on the evaluation of the signals should occur. Such disruptive remanence phenomena, however, occur due to the not absolutely remanence-free ferromagnetic materials of the flux pickups (Hall generators and, under certain conditions, antennas coupled thereto) given field changes, for example, given a change of location of the reception system in the earth's magnetic field or given approach of a measuring instrument with a further field generator.
An example of employment can be seen in gnathology, where one wishes to detect and record the motion of the lower jaw of a person with the assistance of a measuring device. The proposed measuring method provides that a magnetic field generator, for example a permanent magnet, be secured to the lower jaw of a patient and, at a distance from the magnetic field generator, a flux pickup system with Hall generators and antennas be arranged on the head of the patient. The field changes occurring given a motion of the lower jaw are detected by the pickup system in all three planes of motion and are evaluated via an electronic evaluation means. The structure of such a device is described in the German patent application P No. 28 42 764.2 or, respectively, P No. 28 14 551.9, and in the corresponding U.S. Applications Ser. No. 025,263 filed Mar. 29, 1979, and Ser. No. 100,146 filed Dec. 4, 1979 now U.S. Pat. No. 4,303,077 issued Dec. 1, 1981.
In order, in particular, to obtain clear and reproducible measuring results given such measuring devices, it is necessary that no disruptive remanence phenomena changing the initial point (zero point) of the measuring system occur.
Since, however, practically no absolutely remanence-free ferromagnetic materials exist for the flux pickups (Hall generators and antennas) and the earth's magnetic field also has a disruptive effect on the measuring operation, one must strive to eliminate the influence of the remanence.
A conceivable way to eliminate these disruptive remanence phenomena would be a demagnetization of the flux pickups. Such a way is revealed in the publication "Kuhrt/Lippmann, Hallgeneratoren", Springer-Verlag 1968, pages 32, 33. The method for this is to allow a magnetic alternating field with an amplitude H&gt;H.sub.s to influence the ferromagnetic material and to then gradually decrease the amplitude of this alternating field. The magnetization thus circles the coordinate origin in hysteresis loops which become smaller and smaller and finally, given a disappearing alternating field amplitude, achieves the point H=0, M=0.
No external field can have an influence given this demagnetization method, which involves a relatively great expenditure of time. A precise demagnetization, thus, is only possible in a field-free space. In order to avoid the earth's magnetic field, a demagnetization is accordingly only possible perpendicular to the earth's magnetic field and without a measuring magnet. This method, thus, is not suitable for many use cases.